Substantial attention has been directed to the design, implementation, and use of array-based electronic systems for carrying out and/or monitoring biological systems. For example, electronic biosensors of various types have been used to monitor the progress of certain biological systems. Biosensors have been described that include an array of electrode test sites in electrical connection with a plurality of conductive leads. The electrode test sites can be formed in a semiconductor wafer using photolithography and etch processing techniques. Further, the test sites can be coupled to associated detection circuitry via transistor switches using row and column addressing techniques employed, for example, in addressing dynamic random access memory (DRAM) or active matrix liquid crystal display (AMLCD) devices.
There are ongoing efforts to increase the density of electrode arrays by reducing electrode and overlying lead or contact sizes to nanometer- or micrometer-scale dimensions, thereby producing “microelectrode arrays” (MEAs). However, it has been difficult to produce MEAs with very small dimensions using current top-down semiconductor fabrication methods. For example, current photolithography and etch techniques can be employed to pattern openings or vias in an insulation layer formed above the electrodes before filling those vias with a conductive material to form contacts to the electrodes. However, the ability of the photolithography and etch techniques to pattern small features is restricted by factors such as the resolution limits of the optical lithography system. It would therefore be desirable to develop a method for producing a large number of electrode arrays of relatively small dimensions at a relatively low cost.